The department has declined our interview requests, so we can't ask them, but we do know that blood and urine analysis have different uses when it comes to drug testing.

The Minnehaha County Sheriff's Department does not use catheters to extract urine samples, but it collects and tests hundreds of voluntary urine samples every month as part of its 24/7 Sobriety drug-testing program.

Sheriff Mike Milstead, who oversees the program, said blood tests show what's currently in a person's system and how much. They're especially helpful in drunken driving cases to help determine how much alcohol a person has consumed, he said.

Urine tests give investigators a longer term but less precise snapshot of whether a person has used drugs in the days leading up to the test. They're also faster and cheaper than blood tests, offering instant results in some cases and costing around $45 per test compared to $100 for blood tests.

Pennington County State's Attorney Mark Vargo said either a blood draw or urine analysis would be effective for prosecuting someone under the state's criminal ingestion law, which makes it a crime to have illegal drugs present in your system.

Vargo said if his office is concerned about a person's present state at the time of an alleged offense, they prefer a blood draw. If his office is interested in the last several days, he said, a urine analysis would produce a better result.

"The urine analysis is less precise, but easier to collect and is of more historical value," Vargo said.